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--- damped_compound_pendulum [2018/10/17 15:15] – [LEGO DCP] sangsinpark
+++ damped_compound_pendulum [2018/10/17 17:14] – [Final Words] sangsinpark
@@ Line 190: / Line 190: @@
 ===== LEGO DCP =====
-You can make a LEGO version DCP with LEGO bricks, a motorized propeller, and a HiTechnic angle sensor. Even if the angle sensor's resolution is not good (1 degree accuracy), a LEGO DCP control does not matter.
+You can make a LEGO version DCP with LEGO bricks, a motorized propeller, and a HiTechnic angle sensor. Even if the angle sensor's resolution is not good (1-degree accuracy), a LEGO DCP control does not matter.
 {{ dcp:lego_dcp.jpg?500 |}}
 === LabVIEW block diagram for PID control ===
 A LabVIEW program, which is similar to the before LabVIEW code, is employed to control the LEGO DCP at a control frequency of 40Hz. The P, I, and D gain are 0.05, 0.8, and 0.05, respectively.
+Here is the LabVIEW file. {{dcp:lego_dcp_labview_02.zip?linkonly}}
 {{ dcp:lego_dcp_labview_block_diagram.jpg |}}
 In addition, here is the front panel of the LabVIEW program.
@@ Line 201: / Line 204: @@
 A breakdown of the LabVIEW block diagram is shown as follows.
-== Initialize an angle sensor ==
+. Initialize an angle sensor
+{{ dcp:lego_dcp_init_angle.jpg |}}
+Before while loop, reset angle sensor and wait until its angle is within 1 degree.
+. Read angle
+{{ dcp:lego_dcp_read_angle.jpg |}}
+An angle from the angle sensor is measured in the range 0 to 359 degrees with 1-degree accuracy. To display angle in the range -180 to 180, when the angle is greater than 180, subtract 360 from that. Moreover, to avoid getting mixed up with wires, I assign a local variable for the Angle.
-== Read an angle sensor ==
+. PID controller
+{{ dcp:lego_dcp_pid.jpg?500 |}}
+If a control frequency is changed, a value of dt also needs to be changed to a value of 1/frequency.
-== PID controller ==
+. Convert angle to motor power
+{{ dcp:lego_dcp_conversion.jpg |}}
+A constant of 68.98519 is a proportional gain to convert from angle to motor power and another constant of 10 is bias for dead-zone. Those constants can be determined by curve-fitting (see the **Modeling** section).
-== Convert angle to power ==
+. Input motor power
+{{ dcp:lego_dcp_motor.jpg?300 |}}
+For safety and to limit motor rotation to a single direction, a motor power is constrained by in the range of 0 to 100.
-== Input motor power ==
+** NB: If motor terminals are hooked up to an oscilloscope, a motor power range becomes strange. The motor power is in the range -100 to 100. Zero power is not zero anymore. For example, at -100, a motor doesn't rotate and at 0, it can rotate. **
-== Save time and angle ==
+. Save time and angle
+{{ dcp:lego_dcp_save_data.jpg?700 |}}
+To calculate experiment time, read a current time before while loop, and then subtract the time from a time updated in while loop. Lastly, two local variables, Time and Angle, are written into a file after press a STOP button.
 === Exp. #1 - 40 degrees step command and disturbances ===
@@ Line 221: / Line 238: @@
 ===== Final Words =====
-This tutorial's objective was to understand a second order system.
+This tutorial's objective is to understand a second order system through a compound pendulum with a motorized propeller referred to as Damped Compound Pendulum (DCP) and I share my efforts in detail regarding two different DCP realization. PID control of a DCP is successful and then a LEGO version DCP is made for control class and hands-on lab. Eventually, the LEGO DCP is also controlled well.
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 For questions, clarifications, etc, Email: <[email protected]>